In the conventional stencil printing device, printed printing paper is ejected from a printing unit, and is stacked up on a paper ejection table provided in a terminal end of a paper ejection passage, with its printed face up.
If the leading edge of the printing paper droops down as the paper sheet is conveyed to the paper ejection table, the leading edge of the printed printing paper may slide over the upper surface or the printed surface of the paper sheet previously stacked up on the paper ejection table, and this will smear the printed image of the printed printing paper previously placed on the paper ejection table. Therefore, it is proposed, for instance, in Japanese patent publication (kokoku) No. 58-46428, Japanese utility model laid open publication (kokai) No. 60-165347 and Japanese patent laid open publication (kokai) No. 61-217461, to increase the apparent rigidity of the printing paper along the direction of paper ejection (the longitudinal direction) and prevent the leading edge of the printing paper from drooping during the process of paper ejection by providing a lifting member in an intermediate part of the paper ejection passage leading to the paper ejection table and providing a U-shaped or W-shaped curvature to the printing paper as seen in the cross section perpendicular to the direction of paper ejection.
However, the inventors have realized that the effective rigidity of printing paper heavily depends on the thickness, material and size of the printing paper, and that the curvature that should be given to the printing paper for achieving a desired apparent rigidity varies a great deal depending on the type and size of the printing paper. In particular, it has been realized that a fixed lifting member is not adequate in ensuring a Satisfactory operation of the paper ejection device when printing paper of different types and sizes is used on the stencil printing device.
For instance, the effective rigidity of printing paper heavily depends on the size, in particular the lateral width of the printing paper, and it is therefore desirable to determine the degree of the curvature according to the lateral width of the printing paper or the dimension of the printing paper in the direction perpendicular to the direction of paper ejection.
Also, printing paper of a relatively small thickness has a relatively low rigidity, and therefore requires a greater curvature for it to be provided with a required rigidity along the direction of paper ejection or for it to be prevented from drooping. On the other hand, when the printing paper has a relatively large thickness, it already has an almost sufficient rigidity by itself, and, therefore, is not required to be given with a large curvature. As a matter of fact, it is not desirable to give the printing paper a greater curvature than required because it may be detrimental in smoothly ejecting printed printing paper.
In some stencil printing devices, the terminal end of the paper ejection passage is optionally connected to a sorter including a means for positively conveying printing paper such as a belt conveyer instead of a paper ejection table for sorting a plurality of copies made from multiple page originals.
In such a stencil printing device, the lifting member can effectively act upon the ejected printing paper when paper ejection is made onto a paper ejection table. However, when a sorter is connected to the stencil printing device, producing a curvature in the ejected printing paper by means of a lifting member may prevent the positive printing paper feeding means in the sorter from carrying out a satisfactory conveying action, and may cause paper jamming in the sorter.
According to the conventionally known paper ejection device, the lifting member is either fixedly mounted or detachably mounted. When the lifting member is fixedly mounted, it is not possible to readily change the height of the lifting member or to replace the lifting member. When the lifting member is detachably mounted, the user could change the height of the lifting member by replacing it with another. However, as it is normally carried out by the user, the replacing of the lifting member may not be carried out in an appropriate manner. In particular, when the replacement of the lifting member is not appropriately carried out so as to be compatible with the presence of a sorter, an even worse result can be produced.
Furthermore, since the replacement of the lifting member is carried out manually, the work involved may not be slight, and it may impose a serious burden on the user. This is a major factor in reducing the market acceptability of the stencil printing paper as a piece of equipment that is to be widely used in office environments.